Dynamic Virtual Private Network (DVPN) can collect, maintain and distribute information such as public network addresses through a next Hop Resolution Protocol (NHRP) or a Virtual Private Network (VPN) Address Management (VAM) protocol. In the DVPN, VPNs can be established among various branches in the condition that each branch uses a dynamic address to access a public network.
At present, in the DVPN, there is a request of implementing network address translation (NAT) in network communication. During a NAT process, an IP address in a packet head is translated into another IP address.
The NAT can be implemented through a dynamic way. For the dynamic way, an address mapping relationship of a private network and an external network is generated during a process of establishing a connection. In order to sufficiently use IP address resource and to implement that more host computers in the private network can access the external public network at the same time, a port address translation (PAT) mode is adopt for the dynamic way.